The major objective of this project is to establish genetic relationships, by DNA homology experiments, among broad groups to bacteria isolated from the oral cavities of both normal individuals and those with periodontal disease. A second objectve is to investigate the oral microbiota in terms of the specific strains existing in the mouth. The third objective is to determine the distribution of plasmids among strains of the various DNA homology groups. The major groups of bacteria that will be investigated will be Bacteroides and Fusobacterium. DNA homology studies will be completed on the B. oralis (like) and other Bacteroides strains that do not belong to the B. melaninogenicus and B. ruminicola (like) groups. DNA homology studies of Fusobacterium nucleatum, taxonomic and ecological, will be completed and DNA homologies on all other oral Fusobacterium groups will be initiated. The distribution and characterization of plasmids among oral Bacteroides groups (B. melaninogenicus and B. gingivalis) will be in progress.